Missouri has a high breast cancer mortality rate, as well as high rates of type 2 diabetes, cardiovascular disease (CVD), and hypertension, which present more often in individuals who are poor, those living in rural areas, African Americans, and older adults. Women with comorbidities at the time of breast cancer diagnosis may have a worse prognosis, so researchers assessed survival disparities among these patient populations. According to the findings presented at the San Antonio Breast Cancer Symposium on December 5, 2018, comorbidities can negatively impact overall breast cancer survival.

Researchers identified 31,133 adult women with invasive breast cancer diagnosed between 2004 and 2012 from the Missouri Cancer Registry and Missouri Patient Abstract System. Researchers assessed patient race, neighborhood poverty level, residence (rural versus urban), and age at diagnosis. Each patient received a comorbidity score.

After a median follow-up of 79 months, 9,912 deaths occurred, 4,900 of which were because of breast cancer.

Increasing comorbidities significantly impacted breast cancer mortality (p < 0.001). Women with two or more comorbidities had significantly higher breast cancer mortality (hazard ratio [HR] = 1.33; 95% confidence interval [CI] = 1.19–1.49) and all-cause mortality (HR = 1.51; 90% CI = 1.32–1.61). CVD was associated with the largest increase in breast cancer mortality (HR = 1.36; 95% CI = 1.19–1.55).

Researchers did not observe significant differences related to race, poverty, residence, or age; however, age had a statistically significant interaction when modeled as a continuous measure, comorbidity score, and risk of mortality outcomes (p < 0.001).

Caucasian women with all three comorbidities had the highest risk of death (breast cancer-specific: HR = 1.95; all-cause: HR = 2.28). Women in rural areas with two or more comorbidities were 1.78 times more likely to die from breast cancer, whereas women living in metropolitan areas with all three comorbidities were almost two times more likely to die from any cause.